Exemplary embodiments of the invention relate to a device for de-icing and/or for preventing ice formation for an aircraft, comprising a heat emitting device for emitting heat at a surface region of the aircraft. Furthermore, exemplary embodiments of the invention relate to an aerodynamic profile element for an aircraft, e.g. a wing or a part of a wing, an engine intake, or a fin of a tail, which is provided with such a device. In addition, exemplary embodiments of the invention relate to an aircraft having such a device and/or such a profile element. Finally, exemplary embodiments of the invention relate to a method for de-icing a surface region of an aircraft and/or for preventing the formation of ice on the surface region of the aircraft by introducing thermal energy at the surface region.
Ice forms at exposed locations of aircraft, such as front edges of wings, tails, horizontal stabilizers, or engine takes, when the aircraft, such as an airplane, flies through a cloud which contains super-cooled water droplets and/or when droplets/moisture strike a super-cooled aircraft structure. If a layer of ice grows, it impairs the airstream over the affected surface. If the layer becomes large enough, e.g. lift problems or handling problems for the aircraft can result.
Ice protection systems for aircraft are already in use in order to prevent such a formation of ice. Most ice protection systems are designed as anti-ice systems for preventing the formation of ice. Heating systems integrated in the structure are usually provided for this purpose. During flight in icing conditions, wing edges are heated, e.g. with hot bleed air or compressor bleed air, or are heated by electric heaters in the wing edges. In addition, pneumatically operated de-icing devices are used, primarily in smaller airplanes, which inflate rubber mats or rubber tubes integrated on the leading edge of the wing at regular intervals, thereby detaching ice that has accumulated.
In this connection, the conventional de-icing measures are associated with high energy expenditure during the flight. The energy expenditure required to free surfaces of aircraft from ice amounts to approximately 240 to 260 kW of bleed air power or approximately 130 to 150 kW of electric heat output for a surface area to be de-iced of approximately 12 to 15 m2. In the case of bleed air, these data correspond to power per unit of surface of approximately 18.5 kW/m2 or approximately 10 kW/m2 for electric heat.
Known systems or devices for removing ice accumulations during flight on aerodynamically efficient surfaces can be generally subdivided into pneumatic, thermal, and mechanical de-icing systems. An exemplary device for the pneumatic de-icing of surfaces on aircraft is disclosed in European patent document EP 0 658 478 B1. US patent document U.S. Pat. No. 6,702,233 B1 discloses a device for de-icing or preventing the formation of ice on surface regions of aircraft using warm bleed air from the engine.
German patent document DE 10 2010 045 450 B4 discloses an arrangement for de-icing a surface region of an aircraft by irradiating the surface region with a laser.
Other devices for de-icing and/or for preventing the formation of ice employ thermal de-icing by using electric heating elements. It is known, in particular, to prevent the surface of a wing profile from icing by supplying heat to a large surface area by means of an electro-thermal heating mat. An example of such a thermal de-icing is described in European patent document EP 1 017 580 B1.
The method of operation of such known devices for de-icing and/or for preventing ice formation for an aircraft having is described in greater detail by reference to the depictions in FIGS. 6 and 7.
FIGS. 6 and 7 show an aerodynamic profile element 108, for example a wing of an aircraft designed as an airplane, which comprises a known device 100 for de-icing and/or for preventing the formation of ice. The device 100 is provided with a heat emitting device 102 for emitting heat at a surface region 104 of the aircraft 106. The heat emitting device 102 comprises a heating mat 110, which is disposed over a large surface area of the surface region 104 and heats the entire surface region 104. It is thereby possible, for example, to maintain the entire surface region 104 located around the leading edge 112 or around a stagnation line 114 free of ice.
FIG. 6 shows a schematic diagram of a fully evaporative, electro-thermal de-icing system 116 as an example of the known device 100 for de-icing and/or for preventing the formation of ice, said de-icing system 116 being provided with a heating mat 110 in the region of the leading edge 112 of a wing in order to totally prevent ice accumulation over a large surface area by water droplets striking the surface of the wing profile.
By supplying heat over a large surface area using the electro-thermal heating mat 110, the surface of the wing profile can be prevented from icing in the following two ways. It is hereby assumed that the electro-thermal de-icing system 116 is operated permanently:                As depicted in FIG. 6, the water droplets striking the wing profile—profile element 108—are completely evaporated in the fully evaporative de-icing mode.        As depicted in FIG. 7, the adhesion and solidification of water droplets to form ice accumulations on the leading edge 112 of the profile of the profile element 108 are prevented by means of a “running-wet” de-icing mode. The surface temperature of the leading edge 112, which results from the heating by means of this de-icing mode, is lower than in the fully evaporative de-icing mode. As a result, the solidification of the impinging water droplets to form ice is initially prevented on the heated wing leading edge 112. The water droplets run along the wing profile of the profile element 108 in the direction of the trailing profile edge and solidify in less critical, unheated regions on the wing profile to form ice 118.        
In the known electro-thermal de-icing systems 116, it is therefore necessary to either apply very large amounts of energy in order to implement the fully evaporative de-icing mode or, if lesser amounts of energy are used, ice forms on less critical, non-heated regions.
Furthermore, devices for de-icing and/or for preventing the formation of ice are also known that are hybrid devices offering a plurality of possibilities for de-icing, in particular such as the use of thermal energy and mechanical deformation. Examples of known hybrid de-icing systems are known from the following references:                G. Fortin, M. Adomou, J. Perron, “Experimental Study of Hybrid Anti-Icing Systems Combining Thermoelectric and Hydrophobic Coatings”, SAE International, Warrendale, Pa., 2011: This publication discusses an electro-thermal anti-icing system in combination with ice-repellent surface coatings for reducing the amount of energy required for de-icing. In this system, heat is supplied over a large surface area in order to protect the entire surface affected by ice accumulation. The disadvantage of the system, therefore, is the fact that the permanent operation of the anti-icing system—which must be installed over a large surface area—in the region of the entire leading edge of the wing invariably results in high energy consumption.        US patent documents U.S. Pat. No. 5,921,502 and US 2012/0091276 A1, as well as K. Al-Khalil, T. Ferguson, D. Phillips, “A Hybrid Anti-icing Ice Protection System”, AIAA 97-0302 (1997): These publications discuss a hybrid de-icing system from Cox & Company, Inc., which consists of a thermal “running-wet” anti-icing subsystem and a subsystem based on electro-expulsive actuators (EMEDS). The thermal subsystem covers the region of the droplet impact on the leading edge of the wing across a large surface area, either partially or completely. The thermal subsystem therefore has the disadvantage that a relatively large surface portion of the leading edge region of the wing must be heated in order to transport the water droplets further downstream. There, the droplets that have solidified to form ice accumulation can be periodically removed by means of the EMEDS actuators. A further disadvantage of the known hybrid system is the size of the EMEDS actuators. The de-icing system comprising EMEDS actuators has a particularly disadvantageous effect on the electromagnetic compatibility with other systems and components of an aircraft, since very high currents are briefly required for the pulse triggering of the actuators. Moreover, these briefly required, very high currents require a so-called ‘Energy Storage Bank’ (ESB), the weight of which has an extremely disadvantageous effect on the aircraft to be de-iced.        In the case of the de-icing system known from US patent document U.S. Pat. No. 6,283,411 B1 as well, a large surface-area thermal heater is combined with a voluminous and heavy mechanical actuator.        
Reference is furthermore made to the technological background of the following documents [1] and [2]:    [1] K. Al-Khalil, Effect of Mixed Icing Conditions on Thermal Ice Protection Systems, [Apr. 15, 2013], http://www.coxandco.com/files/pdf/FAA-D9688.pdf.    [2] K. Al-Khalil, Thermo-Mechanical Expulsion De-icing System—TMEDS, [Apr. 15, 2013], http://www.coxandco.com/files/pdf/AIAA-2007-0692.pdf.
In general, all the known systems require that substantially high amounts of energy be used for de-icing or to prevent the formation of ice.
Exemplary embodiments of the present invention therefore are directed to a device and a method for de-icing and/or for preventing the formation of ice, with which de-icing and/or prevention of the formation of ice can be carried out using lesser amounts of energy.
In accordance with exemplary embodiments of the present invention an aerodynamic profile element that is provided with such a device, such as, for example, a part of an airfoil or a fin or an engine intake of an aircraft, and an aircraft provided with such a device or such a profile element.
According to a further aspect, exemplary embodiments of the invention involve a method for de-icing and/or for preventing ice formation for an aircraft.
One advantage of the invention is that a device and a method for de-icing a surface region of an aircraft and/or for preventing the formation of ice on the surface region of the aircraft are created by the targeted introduction of thermal energy into a defined surface region.
A particular advantage of preferred embodiments of the invention is the creation of a device and a method for de-icing and/or for preventing the formation of ice, with which de-icing and/or prevention of the formation of ice is made possible such that electromagnetic compatibility of the de-icing device and the systems of the aircraft is ensured. A substantial advantage of such embodiments as compared to known systems is that briefly high currents for pulse triggering of the surface of a profile element to be de-iced are not required.
According to a first aspect, the invention creates a device for de-icing and/or for preventing ice formation for an aircraft, the device comprises a heat emitting device for the targeted emission of heat at a defined surface region of the aircraft, wherein the heat emitting device is designed to emit heat along the shape of a line in order to produce a predetermined breaking point or a predetermined breaking line in ice accumulating on the surface region.
The heat emitting device is preferably designed such that it emits heat in a defined line-shaped heat emission region having a line width in the range of 0.2 mm to 4 mm, preferably 0.5 mm to 1.5 mm and, most preferably, approximately 1.0 mm or approximately 0.8 mm or in the range of approximately 0.8 mm to approximately 1.0 mm.
The line-shaped heat emission region preferably extends, via the longitudinal direction thereof, along the stagnation point line of a profile element of the aircraft to be de-iced or to be maintained free of ice. The stagnation point line is preferably located substantially in the center within the line-shaped heat emission region.
Preferably, the attachment of the heat emitting device on the inner side of the surface of the profile body is implemented by a materially bonded connection, in particular an adhesive bond. In a preferred design, the connection, such as the adhesive bond, in particular, has a length about the stagnation point of the profile element in the range between 0.5 mm and 1.5 mm, and, in an explicitly good design, a length of 0.8 mm. In a preferred design, the thickness of the adhesive bond is 0.2 mm.
Preferably, the heat emitting device has a preferably line-shaped heat source. The heat source is preferably enclosed by an insulating jacket in order to reduce or prevent heat from radiating into the interior of the profile element. In a preferred design, the insulating jacket is made of Kapton, for example, which has low thermal conductivity and therefore has a good insulating effect. In an alternative design, the insulating jacket can also be made of another highly thermally insulating material or a plurality of various highly thermally insulating materials. Moreover, the insulating jacket of the heat source enables the heat emission to be bundled inside the jacket, thereby allowing the heat to be introduced into the surface of the profile element in the shape of a line. The effect of the heat buildup that is produced as a result also serves to reduce energy consumption. The insulating jacket preferably comprises a line-shaped opening for the formation of the heat emission line.
The device is preferably designed as a hybrid device for de-icing and/or for preventing the formation of ice by means of thermal and mechanical energy.
A preferred embodiment of the device comprises a deformation device for the deformation of at least one part of the surface of the surface region.
Preferably, the heat emitting device comprises at least one preferably elongated heat source and an insulating jacket for the heat source for preventing heat radiation at region other than the heat emission line.
The deformation device preferably comprises at least one piezoelectric actuator or an arrangement of piezoelectric actuators for deforming a surface of the surface region.
In a further preferred embodiment, the deformation device can comprise at least one inertial force generator or an inertial mass oscillator. The inertial force generator or the inertial mass oscillator can be provided in addition or as an alternative to the at least one piezoelectric actuator.
The heat emitting device preferably contains an insulating jacket, which prevents heat from the heat source, for example the heating wire that rides out in a planar manner from radiating into the surface of the profile element.
Preferably, the heat emitting device contains an insulating jacket, which prevents the heat emitted by the heating wire from radiating into the interior of the profile element and thereby ensures a buildup of heat that is introduced into the surface of the profile element in the shape of a line.
An ice detection device is preferably provided, which is designed to detect an accumulation of ice on the basis of information received by the heat emitting device and/or by at least one actuator.
The at least one piezoelectric actuator is preferably designed as a d33 stack actuator.
The extension direction of the at least one actuator, in particular of the at least one piezoelectric actuator, is preferably oriented in the wingspan direction when used on a profile of a wing. In particular, the extension direction is oriented with at least one directional component in the direction of the heat emission line.
Preferably, the piezoactuators and/or the heating wire or the heating element can be used to detect ice accumulations on the surface. A detection device, in particular, is provided for this purpose, which can detect whether an accumulation of ice is present on the basis of parameters obtained with these elements.
The heat emitting device of the device according to the invention is designed to emit heat along the shape of a line in order to thereby produce a predetermined breaking point or a predetermined breaking line in ice accumulating on the surface region. The heat emitting device is therefore designed to emit heat along a heat emission line. Depending on the energy input, ice located on the heat emission line weakens along said heat emission line, thereby enabling the ice to be fractured, or no ice forms at all along the heat emission line, with the result that, at best, ice can form on sections of the surface region that are separated by the heat emission line. In this connection, the heat emission line preferably has the shortest possible extension in the width direction. The line widths should be a maximum of, e.g. 5 mm, although a substantially narrower heat emission line in the range of 0.2 mm to 3 mm is preferable, and more preferably is in the range of 0.5 mm to 1.5 mm and, most preferably, is approximately 0.8 mm. Heat is emitted in a targeted manner along the shape of a line having a minimal width extension. It is sufficient for the ice to fracture; remaining ice residue can be removed mechanically, which is energy-efficient.
In a particularly preferred embodiment of the device according to the invention, the deformation device comprises a first deformation unit on a first section of the surface region and a second deformation unit on a second surface region, which is separated from the first section by the heat emission line.
The deformation device preferably comprises a first deformation unit on a first side of a heat emission line of the heat emitting device, for deforming a first section of the surface region, which is located on the first side, and comprises a second deformation unit on the second side of the heat emission line for deforming a second section of the surface region, which is located on the second side.
In a particularly preferred embodiment, the device has a surface coating for the surface region, which reduces ice adhesion forces.
Preferably the heat emission device comprises, as the line-shaped heat source, at least one heating wire and/or at least one piezoelectric actuator, which is designed and set up to be capable of emitting heat along the shape of a line.
The heat source of the heat emitting device is preferably enclosed by an insulating jacket in order to prevent heat from radiating into the interior of the profile element and/or to generate a buildup of heat, by means of which heat can be introduced into the surface of the profile element along the shape of a line.
According to a further aspect, the invention involves an aerodynamic profile element for an aircraft, which comprises a device—according to the invention or the advantageous embodiments thereof—for de-icing and/or for preventing the formation of ice.
A preferred embodiment of the profile element is preferably characterized in that the heat emitting device is designed to emit heat along the shape of a line for the purpose of producing a predetermined breaking point or a predetermined breaking line along or near a stagnation line of the profile element and/or along a leading edge of the profile element.
In the case of the profile element, it is also preferable to provide a deformation device, by means of which the at least one part of a surface region of the profile element, which encloses the stagnation line and/or the leading edge of the profile element, can be deformed in order to remove ice.
Particularly preferably, the deformation device comprises the first deformation unit for deforming the first section and the second deformation unit for deforming the second section of the surface region, wherein the sections are preferably separated by the stagnation line and/or the leading edge of the profile element.
Preferably a surface region is provided, which encloses the stagnation line and/or the leading edge of the profile element and has a surface coating, which reduces ice adhesion forces.
The surface region is preferably provided with a nanostructured surface and/or a hydrophobic surface, in particular a super-hydrophobic surface.
According to a further aspect, an aircraft is provided that comprises a device according to the invention or the advantageous embodiments thereof or comprises an aerodynamic profile element according to the further aspect of the invention or the advantageous embodiments thereof.
According to a further aspect, the invention provides a method for de-icing a surface region of an aircraft and/or for preventing the formation of ice on the surface region of the aircraft by introducing thermal energy at the surface region, characterized by the introduction of heat along a line on the surface region in order to form a predetermined breaking line or a parting line in accumulating ice or in collections of water droplets accumulating on the surface region.
According to a further aspect, the invention provides a method for de-icing a surface region of an aircraft and/or for preventing the formation of ice on the surface region of the aircraft by introducing thermal energy at the surface region, characterized by the introduction of heat along a line on the surface region in order to form a predetermined breaking line or a parting line in accumulating ice or collections of water droplets accumulating on the surface region.
A preferred embodiment of the method further comprises the step of:
Deforming the surface region—in particular by means of piezoactuators—in order to fracture ice along the predetermined breaking line and/or to remove ice fractured along the predetermined breaking line and/or to remove accumulating water droplets.
A further preferred embodiment of the method comprises the step of:
Equipping or providing the surface region with a surface coating that reduces ice adhesion forces, and/or with a surface property that reduces ice adhesion forces.
Exemplary embodiments of the invention are designed to emit heat along a heat emission line at a surface region to be de-iced or to be maintained free of ice. Heat is preferably emitted along or in the vicinity of a stagnation line or stagnation point line. As a result thereof, and, in a particularly preferred embodiment, as a result of an insulating jacket of a heat source of a heat emitting device designed to emit heat along the shape of a line, a predetermined breaking line or a parting line can be created between collections of water droplets or ice accumulations that form nevertheless, with relatively little energy input. The ice accumulations that form on both sides of the heat emitting line can therefore be more easily removed.
Particularly preferably, the device is designed as a hybrid de-icing system. The device designed as a hybrid de-icing system makes possible a particularly energy-efficient de-icing of ice that has accumulated during flight.
In a preferred embodiment of the device, hybridization is achieved by                a) targeted use of thermal energy—in particular by means of a heating wire, more particularly by a heating wire enclosed (nearly entirely, with the exception of an opening to form the heat emission line) by an insulating jacket, or by any other heat source that is suitable for emitting heat along the shape of a line—coupled with        b) a deformation of the surface to be de-iced—preferably by means of one or more piezoelectric actuators and/or one or more inertial force generators or inertial mass oscillators—particularly preferably, furthermore, in combination with        c) a surface coating that reduces ice adhesion forces, for example by means of a nanostructured, super-hydrophobic surface, for example by means of hydrobead.        
In a particularly preferred embodiment, the device for de-icing and/or for preventing the formation of ice is formed by a hybrid system, which comprises a combination of three subsystems, namely an electro-thermal system, a mechanical system, and a surface coating. A combination of all three measures has proven to be particularly energy-efficient and has proven to be the most effective solution.
However, the combination of the line-shaped emission of heat with only one of the other subsystems—mechanical deformation or surface coating—also offers considerable energy advantages over known de-icing systems.
In addition, the use of the line-shaped emission of heat along a predefined heat emission line is interesting on its own for de-icing.
Particularly preferably, piezoactuators are provided for deforming the surface region for the purpose of mechanically removing accumulating ice.
Of particular interest is a combination of a heat emission device that emits heat along the shape of a line—for example, in particular, with the aid of a heating wire, which, in a particularly preferred design, is enclosed by an insulating jacket—with a corresponding surface deformation, for example by means of piezoactuators, in particular. Due to a combination of this type, the ice that is mechanically freed from the surface is not held against the surface by aerodynamic forces of the flow, but rather is entirely removed, in particular by means of a punctiform predetermined breaking point (according to a two-dimensional view), which is thermally introduced at the stagnation point, or by means of the line-shaped predetermined breaking point in the wingspan direction (according to a three-dimensional view), which is thermally introduced at the stagnation line.
Further advantages of the device according to the invention—in particular in an embodiment as a hybrid system—are smaller installation space and a reduction in the weight of the device.
In particular, when the device is structurally integrated into a profile element, for example a wing profile of an aircraft, no moving parts are present, and therefore a long service life can be expected.
Moreover, the use of a heating wire is preferred. This also has advantages in terms of a sensor system. A heating wire that is provided can also be used as a temperature sensor.
In addition, the formation of ice on the surface of the profile body, for example a wing profile, can also be detected by means of piezoelectric actuators, which are provided for deforming the surface, for example by shifting the resonant frequencies or by means of modified oscillation modes.
In this respect, the heating elements and actuators that are utilized can also be used as sensors. Additional sensors are therefore unnecessary, and even more weight can be saved.